How to select the exterior part of the wall fasade?

Hi all,
Is there anyway to define the exterior surface of the wall geometries?
My whole geometry model is imported as mesh in Rhino, i just can have the facade wall geometries separated, but i cannot find a way to select the exterior surface of those walls for the sake of analysis. Is there any tips that might help?

Hi @Niloo have you tried sub-selecting the desired faces with Lctrl+Lshft held while clicking the desired surface.
Also if you want your mesh to be surfaces/breps you can select it and use the rhino command MeshToNURB and then to clean it up: MergeAllCoplanarFaces
Hopefully something in that was helpful
best
-trevor

Hi Trevor, thank you very much for your answer, i am specifically looking for a solution that can solve this in grasshopper. Although the Rhino tips you mentioned are very handy and i am going to use them, but it would be great to be able to manage the building geometry in grasshopper as well.